1. Field of the Invention
The present invention relates to a method of manufacturing a wire harness for automobile use.
2. Discussion of Related Art
An example of the wire harness for automobile use is shown in FIG. 6, which is composed in such a manner that electric wires "a" are arranged in parallel with each other, connectors C are connected to appropriate portions of the electric wires in the longitudinal and the transverse direction, and the connectors C are covered with covers T if necessary.
From the viewpoint of enhancing the working efficiency, the electric wires "a" are frequently connected to the connectors C by means of crimp-style connection, also referred to herein as a crimp connection. As shown in FIG. 7, this crimp-style connection is conducted in the following manner. In the connector, there is provided a crimp-style terminal 41 having a groove 42, the width of which is somewhat smaller than the outer diameter of the electric wire "a". The electric wire "a" is fed into the groove 42 and pushed down by a crimp connecting blade not shown in the drawing, so that the electric wire "a" can be press-fitted into the groove 42. In the case of an electric wire "a" composed of a bundle of conductors 44 and covering material 43 which covers the bundle of conductors 44, the covering material 43 is torn by the wall of the groove 42 when the electric wire "a" is press-fitted into the groove, so that the bundle of conductors 44, which have been exposed, come into contact with the terminal 41 and electrically communicate with the terminal 41. At the same time, the electric wire "a" is fixed into the groove 42 by the action of spring-back of the terminal 41.
In this connection, an intensity of the spring-back action of the terminal 41 and a pushing distance of the electric wire "a" which has been pushed down are relatively related to each other. When the pushing distance of the electric wire "a" is increased, the intensity of the spring-back action of the terminal 41 is increased. However, when the pushing distance of the electric wire "a" is excessively increased, the terminal 41 is plastically deformed, and the intensity of the spring-back action is decreased or further decreased to zero. In the above case, the crimp connection becomes unstable, and the electric wire "a" is disconnected from the terminal 41 even if a low intensity of force is given to the crimp connecting section from the outside or even if the crimp connecting section is somewhat oscillated.
In the same manner, when the pushing distance of the electric wire "a" is too small, the intensity of the spring-back action becomes too low. Also, the crimp connection becomes unstable in this case.
In order to connect the electric wire "a" to the groove 42 with pressure in a stable state by the action of spring-back so that the electric wire "a" can be positively communicated with the terminal 41, it is necessary that the electric wire "a" is pushed into the groove 42 by an appropriate distance. When this crimp connection, in which the electric wire "a" is pushed into the groove 42 by an appropriate distance, is manually conducted by a worker, the pushing distance of the crimp connecting blade fluctuates, that is, when a different worker conducts the crimp connection by pushing the electric wire "a" into the groove 42, the pushing distance fluctuates.
Usually, a plurality of electric wires "a" are connected to one connector C as shown in FIG. 6. When the plurality of electric wires "a" are manually connected by a worker one by one, the pushing distance of the electric wire "a" for each terminal fluctuates even if the same worker conducts this connection.
When the number of electric circuits (the number of electric wires "a") increases, the number of crimp connections also increases. In accordance with the increase in the number of crimp connections, there is a possibility of the occurrence of erroneous wiring. In order to solve the above problems, this crimp connection has been automatized recently.
When an automatic crimp connecting machine is used in the manufacture of the wire harness, the aforementioned fluctuation of connection can be avoided and further the connecting speed can be increased. However, the following problems may be encountered. FIG. 8 shows an example of connections made by connectors and terminals, which are arranged as follows. The connector includes five connectors C.sub.1, C.sub.2, C.sub.3, C.sub.4 and C.sub.5. Connector C.sub.1, has four terminals of T.sub.11 to T.sub.14, connector C.sub.2 has four terminals of T.sub.21 to T.sub.24, and connector C.sub.3 has four terminals of T.sub.31 to T.sub.34. Connector C.sub.4 has three terminals of T.sub.41 to T.sub.43, and connector C.sub.5 has three terminals of T.sub.51 to T.sub.53. Electric wire "a" includes four electric wires of a.sub.1, a.sub.2, a.sub.3 and a.sub.4, which are complicatedly connected to the connectors as shown in the drawing. In order to manufacture the above wire harness, the structure of the manufacturing apparatus becomes complicated and the size of the apparatus is increased. As a result, the manufacturing cost is raised. Therefore, it is impossible to apply the automatic connecting machine to a case in which a large number of types of products are produced, wherein a quantity of each type of product is small.
In an automobile factory in which the number of electronic parts to be incorporated into automobiles is increased day after day, it is an urgent necessity to manufacture various types of wire harness of complicated wiring effectively.